The capercaillie is the world’s largest grouse which, in Scotland, lives in open mature pinewoods. One of our most elusive birds it probably became extinct in Britain in the mid-18th century, largely due to the destruction of native woodland habitat. In 1837, birds from Sweden were reintroduced into Perthshire and by the early 1970s there were thought to be around 20,000 capercaillie in Scotland. However, since then the numbers have fallen dramatically.

Male capercaillie

Thus the capercaillie is of high conservation concern in Scotland as the population has declined to less than 2,000 birds. Strathspey remains the stronghold with around 75% of the Scottish population and was therefore the centre of a recent study looking at their breeding success.

The study produced a report which is the result of a partnership comprising SNH, RSPB Scotland and the Cairngorms National Park Authority (CNPA) and produced some interesting findings.

Native Scots pine woodland

One thing to emerge is that there are complex links to the success of capercaillie in rearing young and the following factors:

habitat structure

predator activity

weather during the egg-laying and brood rearing period.

Some elements of the new report have been found before. In particular the link between poor capercaillie breeding success and wet weather in June (when females have dependent downy chicks).

Female capercaillie

The report also found a weak association between breeding success and a measure of pine marten activity.

One interesting new finding was that blaeberry leaves (a key food item for capercaillie) had a better defence against herbivores through their chemical composition in old-growth Scots Pine forest than in younger plantations.

Adult capercaillie and chicks depend heavily on blaeberry leaves, and their associated insects, as food. However, further work will be needed to test whether forest management could help to increase the quality of blaeberry in forests for capercaillie.

Capercaillie detail

Sue Haysom of SNH welcomed the new report and noted that “This report improves our understanding of the complex relationships between weather, habitat, predators and capercaillie breeding success and how these factors vary across key woods in Strathspey.”

Justin Prigmore of the Cairngorms National Park Authority also commented on the report noting that: “Strathspey is the most important area in Scotland for the species and is the only area where numbers have remained relatively stable. It is essential that we do all we can to ensure their long-term survival here. This work shows that it is a complicated picture but helps direct where we need to focus effort for the future and will further inform the Cairngorms Capercaillie Framework which is working across this landscape scale.”

The capercaillie is not an easy bird to see and is very sensitive to disturbance so if you want a chance of seeing this special bird without risking disturbing them check out Caper Watch which continues till mid-May at the RSPB’s Osprey Centre at Loch Garten.